feat: implement output formatting and display (HAN-383)

Add text and JSON formatters with real-time progress via traverser hooks,
summary statistics, and CLI integration for --show-* and --json flags.

Co-authored-by: multica-agent <github@multica.ai>

internal/output/stats.go

@@ -0,0 +1,187 @@
+package output
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/hits/ExploreDNS/internal/dns"
+	"github.com/hits/ExploreDNS/internal/traverse"
+	miekgdns "github.com/miekg/dns"
+)
+
+type summaryEntry struct {
+	Type string
+	Prob float64
+}
+
+type answerEntry struct {
+	RData string
+	Prob  float64
+	RRs   []string
+}
+
+type SummaryStats struct {
+	ByType  map[string]float64
+	Answers []answerEntry
+}
+
+func ComputeSummary(results []traverse.TraversalResult) *SummaryStats {
+	stats := &SummaryStats{
+		ByType: make(map[string]float64),
+	}
+
+	for _, result := range results {
+		if result.Response == nil || !result.Response.IsTerminal() {
+			continue
+		}
+		if result.Referral == nil {
+			continue
+		}
+
+		prob := result.Referral.Prob
+		respType := result.Response.Type.String()
+
+		switch result.Response.Type {
+		case traverse.RespAnswer:
+			key, rrs := answerKey(result.Response)
+			if key == "" {
+				stats.ByType[respType] += prob
+				continue
+			}
+			found := false
+			for i := range stats.Answers {
+				if stats.Answers[i].RData == key {
+					stats.Answers[i].Prob += prob
+					found = true
+					break
+				}
+			}
+			if !found {
+				stats.Answers = append(stats.Answers, answerEntry{
+					RData: key,
+					Prob:  prob,
+					RRs:   rrs,
+				})
+			}
+		default:
+			stats.ByType[respType] += prob
+		}
+	}
+
+	sort.Slice(stats.Answers, func(i, j int) bool {
+		return stats.Answers[i].RData < stats.Answers[j].RData
+	})
+
+	return stats
+}
+
+func answerKey(resp *traverse.Response) (string, []string) {
+	if resp == nil || resp.Decoded == nil {
+		return "", nil
+	}
+
+	var rdatas []string
+	var formatted []string
+	for _, rr := range resp.Decoded.Answers {
+		if _, ok := rr.(*miekgdns.CNAME); ok {
+			continue
+		}
+		rdata := rrDataString(rr)
+		if rdata == "" {
+			continue
+		}
+		rdatas = append(rdatas, rdata)
+		formatted = append(formatted, dns.FormatRecord(rr))
+	}
+
+	if len(rdatas) == 0 {
+		return "", nil
+	}
+	sort.Strings(rdatas)
+	return strings.Join(rdatas, " / "), formatted
+}
+
+func rrDataString(rr miekgdns.RR) string {
+	switch v := rr.(type) {
+	case *miekgdns.A:
+		return v.A.String()
+	case *miekgdns.AAAA:
+		return v.AAAA.String()
+	case *miekgdns.CNAME:
+		return v.Target
+	case *miekgdns.NS:
+		return v.Ns
+	case *miekgdns.MX:
+		return fmt.Sprintf("%d %s", v.Preference, v.Mx)
+	case *miekgdns.TXT:
+		return strings.Join(v.Txt, " ")
+	default:
+		return rr.String()
+	}
+}
+
+func formatProbability(prob float64) string {
+	text := fmt.Sprintf("%.1f%%", prob*100)
+	text = strings.Replace(text, ".0%", "%", 1)
+	return fmt.Sprintf("%5s", text)
+}
+
+func summaryTypeLabel(respType string) string {
+	switch respType {
+	case "nodata":
+		return "found no such record"
+	case "nxdomain":
+		return "name does not exist"
+	case "servfail":
+		return "resulted in SERVFAIL"
+	case "error":
+		return "resulted in an error"
+	case "referral":
+		return "resulted in a referral"
+	default:
+		return respType
+	}
+}
+
+func trimDomain(name string) string {
+	return strings.TrimSuffix(name, ".")
+}
+
+func collectServers(results []traverse.TraversalResult) map[string][]string {
+	servers := make(map[string][]string)
+	for _, result := range results {
+		if result.Response == nil || result.Response.Server == nil {
+			continue
+		}
+		name := serverName(result)
+		ip := result.Response.Server.String()
+		if containsString(servers[name], ip) {
+			continue
+		}
+		servers[name] = append(servers[name], ip)
+	}
+	return servers
+}
+
+func serverName(result traverse.TraversalResult) string {
+	if result.Referral != nil && result.Referral.Bailiwick != "" && result.Referral.Bailiwick != "." {
+		return trimDomain(result.Referral.Bailiwick)
+	}
+	if result.Referral != nil && result.Referral.NSName != "" {
+		return result.Referral.NSName
+	}
+	if result.Response != nil && result.Response.Server != nil {
+		return result.Response.Server.String()
+	}
+	return "unknown"
+}
+
+func containsString(items []string, target string) bool {
+	for _, item := range items {
+		if item == target {
+			return true
+		}
+	}
+	return false
+}